Business Tax Deductions: What the IRS Actually Audits

In order of typical dollar impact for small businesses:

1. Cost of goods sold (COGS): direct costs of products or services sold. Fully deductible without limits.
2. Office rent and utilities: 100% deductible for business-use spaces. Home office portion if applicable.
3. Employee and contractor payments: wages, benefits, payroll taxes, 1099 payments all deductible. Major source of deductions for service businesses.
4. Vehicle expenses: either standard mileage ($0.70/mile for 2025) or actual expenses. Subject to business-use percentage.
5. Equipment and depreciation: Section 179 allows immediate expensing up to $1.16 million per year (2025 limit). Bonus depreciation handles additional amounts.

Less obvious deductions that add up:

• Business insurance premiums
• Legal and professional fees
• Subscriptions and software
• Training and education (if related to current business)
• Business banking fees
• Advertising and marketing
• Office supplies and materials
• Telecommunications (business portion)
• Shipping and postage
• Business meals (50% deductible)
• Retirement plan contributions (SEP-IRA, Solo 401(k))
• Health insurance premiums (self-employed deduction)

The home office deduction is one of the most valuable for self-employed and small business owners, but also one of the most audited. Two methods:

Simplified method: $5 per square foot of home office space, up to 300 sq ft ($1,500 maximum). No detailed records required. Safe and simple.

Actual expense method: calculate the percentage of your home used exclusively for business, then deduct that percentage of home expenses (mortgage interest, property tax, utilities, insurance, repairs, depreciation). Can be significantly larger than the simplified method.

Requirements for both methods:

• Exclusive use: the space must be used ONLY for business. A kitchen table that doubles as a dining area doesn't qualify.
• Regular use: you must use the space regularly, not just occasionally.
• Principal place of business OR meeting clients: the home office must be your principal place of business, or a place where you meet with clients/customers.

Audit triggers:

• Large actual-method deductions (over $5,000/year) without corresponding utility bills or supporting records
• Home office deduction combined with outside-of-home workspace claims
• Documentation showing mixed personal/business use

The simplified method is lower risk and adequate for most taxpayers. Use actual expenses only if you have substantial home expenses and well-documented exclusive use.

Vehicle expenses are the most frequently audited small business deduction because they're easy to abuse. Two methods:

Standard mileage: $0.70 per business mile (2025 rate). You must track mileage with a contemporaneous log (odometer readings, dates, destinations, business purpose).

Actual expenses: deduct the business-use percentage of all vehicle costs (gas, insurance, maintenance, depreciation, registration). Requires detailed records of all expenses plus mileage log to establish business percentage.

Documentation requirements:

• Mileage log: date, starting and ending odometer readings, destination, business purpose. Required for both methods.
• Receipts: all vehicle-related expenses if using actual method
• Total miles vs business miles: establishes business percentage

Common audit traps:

• "Commuting" claimed as business miles. Commuting from home to a regular work location is NOT deductible. Home-to-client or between business locations is deductible.
• 100% business use claimed on a single vehicle. Very rare and heavily scrutinized.
• Round numbers on mileage log. "500 miles per week" looks suspicious. Real logs have odd numbers and variance.
• Creating the log after the fact. Contemporaneous logs are required; reconstructing from memory is subject to challenge.

Use a mileage tracking app (MileIQ, Everlance, QuickBooks Self-Employed) that automatically logs trips. This produces defensible documentation and is far easier than manual logs.

The Tax Cuts and Jobs Act of 2017 eliminated the entertainment deduction entirely. Business meals remain deductible with limits:

• Business meals with clients or prospects: 50% deductible. Must be directly related to the business, with a clear business purpose.
• Employee meals (office lunches, employee events): generally 50% deductible, with some exceptions.
• 100% deductible meals (specific cases): meals at company events (holiday parties, picnics), snacks and drinks provided to employees in the office, meals for restaurants' own employees
• Entertainment (tickets, golf, shows): NO longer deductible at all since 2018

Documentation requirements for business meals:

• Amount of the expense
• Time and place
• Business purpose
• Names and business relationships of people present
• Receipt (for expenses over $75)

Keep receipts with notes written on them. "Lunch with John Smith of Acme Corp — discussed project pricing and timeline" is adequate documentation. Just "lunch" is not.

Travel expenses for business trips are 100% deductible (meals during travel are 50%). Qualifying travel:

• Transportation (airfare, rental car, train, taxi, rideshare)
• Lodging (hotels, Airbnb)
• Meals (50% deductible during travel)
• Conference and event fees
• Tips and incidentals

Requirements:

• Primary purpose must be business. If you're at a destination for 7 days and 2 are business, the other 5 days of expenses are not deductible.
• Combined business/personal travel requires allocation. Only the business portion is deductible.
• Spouse travel is generally NOT deductible unless the spouse is also an employee with a legitimate business purpose for the trip.
• Conference attendance qualifies if the conference is relevant to your business and you actually attend sessions.

Audit traps:

• Vacation destinations (Hawaii, Caribbean) with minimal business content claimed as business travel
• Extended stays at tourist destinations with brief business meetings
• First-class travel and luxury hotels without business justification
• Repeated "business trips" to the same location where the owner has personal connections

Document business purpose thoroughly for any travel that could look like a vacation. Save conference registration confirmations, meeting agendas, client contact information.

Certain claims consistently fail on audit despite being commonly attempted:

• Clothing: not deductible unless it's a uniform required by the business and not suitable for everyday wear. Business suits and professional attire are NOT deductible.
• Country club dues: not deductible, even if used primarily for business entertainment.
• Commuting to regular office: not deductible for any taxpayer.
• Personal cell phone: only the business-use portion is deductible. Claiming 100% is usually rejected unless you have a separate personal phone.
• Hobby expenses: if your "business" consistently loses money (generally 3 out of 5 years), the IRS may reclassify it as a hobby, disallowing all business deductions.
• Personal expenses dressed up as business: family vacations, personal meals with family, home improvements in non-business areas of home
• Political contributions and lobbying expenses: not deductible as business expenses

The general rule: the expense must be both ordinary (common in your industry) and necessary (helpful to your business). Many borderline expenses fail one or both tests.